CHATHAM — Researchers call it Shark Cove, a slender slip of sand that dangles like an overstretched strand of taffy from the northern portion of the Monomoy islands, connecting them with the fat teardrop of land known as South Monomoy.

Five miles south of the mainland, this area is where state Division of Marine Fisheries shark researchers Greg Skomal and John Chisholm have been finding great whites lying in wait for the gray seals that gather by the thousands along these isolated beaches.

Skomal's team has tagged two great whites this summer, giving one an acoustic tag that emits a unique identifying signal that is picked up by receivers attached to buoys along the shoreline from Chatham into Orleans.

Monday was an especially good day in spite of a wind that riled up the surface of the sea, making it harder for spotter pilot Wayne Davis circling overhead to pinpoint sharks. But Wigren said that, despite the poor visibility the team was able to find as many as five sharks in about 16 feet of water, two in Shark Cove a few hundred yards off the beach, and two to three a little to the north.

Using a hydrophone, they listened for the unique pinging sequence that would tell them they were tracking a tagged shark. Researchers then lowered miniature underwater cameras into the water to record identifying marks such as mating scars, skin color patterns or the fraying on the trailing edge of the dorsal fin, and to look for claspers, the male sex organ, to determine gender.

If the shark is still around after that, and hasn't already been tagged, they use a short harpoon with a detachable head to fix one of these electronic markers onto its dorsal fin.

This is the first year of a four-year population study that will establish a database of unique marks to be used to identify individuals in the future. Researchers also intend to conduct a mark-and-recapture study that will estimate population numbers based on the ratio of familiar tagged sharks to the overall stock size.

Funded by the Atlantic Great White Shark Conservancy, Skomal and Chisholm, the lead scientists investigating the Cape's great white sharks, have been out 17 times this summer off Chatham, identifying a total of 11 individual great whites thus far. Six of those are new individuals not seen before, Conservancy President Cynthia Wigren said. Five were great whites that had previously been tagged.

The Conservancy originally estimated it would take $30,000 to pay for the spotter plane and other expenses for the first year, but Wigren said that amount is now set at $50,000, with $49,000 already raised through donations and benefits.

The study is expected to go on into October, she said, as long as the weather cooperates.